The present invention relates to an ink ejection apparatus which may be incorporated into a printer for a computer, facsimile system or the like.
An ink ejection apparatus is known in which an ink ejection head is formed with an ink chamber and an ejection orifice communicating with the ink chamber. An electrostrictive plate is provided which defines part of the ink chamber. An electrical pulse applied to the electrostrictive plate causes the same to strain in such a manner as to decrease the volume of the ink chamber and cause ink to be ejected through the orifice. Since the strain is small in magnitude, the apparatus is inoperative if there are air bubbles in the ink in the ink chamber and of course is inoperative if there is no ink in the ink chamber. Since the ink is incompressible, a small reduction of volume of the ink chamber will cause the same volume of ink to be positively displaced out the orifice. However, since air is compressible, such a small reduction in volume of the ink chamber will compress air bubbles in the ink chamber, and the increase in pressure will be insufficient to force ink out of the orifice due to the design of the ejection head. If air bubbles should become present in the ejection head during a printing operation of, for example, computer data, the whole data will not be printed out. Such a malfunction may not be noticed, especially if the printout does not terminate in the middle of a sentence, and may result in a serious error in judgement by the concern utilizing the apparatus due to failure to print out important information.